/**
 * HEIC Image Converter - Refactored with improved error handling and ES6 modules
 */

// Error handling utility
class HeicConversionError extends Error {
  constructor(message, context, originalError = null) {
    super(`HEIC Conversion Error [${context}]: ${message}`);
    this.name = "HeicConversionError";
    this.context = context;
    this.originalError = originalError;
  }
}

// Logger utility for structured error reporting
const logger = {
  error: (message, context, error = null) => {
    const errorInfo = {
      timestamp: new Date().toISOString(),
      context,
      message,
      originalError: error?.message || error,
    };
    console.error(JSON.stringify(errorInfo));
  },
};

// Async utility for generator functions
const asyncGenerator = (context, _args, generator) =>
  new Promise((resolve, reject) => {
    const step = (result) => {
      try {
        const next = generator.next(result);
        if (next.done) {
          resolve(next.value);
        } else {
          Promise.resolve(next.value).then(step, handleError);
        }
      } catch (error) {
        handleError(error);
      }
    };

    const handleError = (error) => {
      logger.error("Async generator failed", context, error);
      reject(new HeicConversionError(error.message, context, error));
    };

    try {
      step(generator.next());
    } catch (error) {
      handleError(error);
    }
  });

// HEIC format detection
export const isHeic = (file) => {
  return asyncGenerator("formatDetection", null, function* () {
    try {
      const buffer = (yield file.arrayBuffer()).slice(8, 12);
      const decoder = new TextDecoder("utf-8");
      const fileType = decoder.decode(buffer).replace("\0", " ").trim();

      const supportedTypes = ["mif1", "msf1", "heic", "heix", "hevc", "hevx"];

      if (!supportedTypes.includes(fileType)) {
        logger.error(`Unsupported file type: ${fileType}`, "formatDetection");
        return false;
      }

      return true;
    } catch (error) {
      throw new HeicConversionError(
        "Failed to detect HEIC format",
        "formatDetection",
        error,
      );
    }
  });
};

// Worker management
let heicWorker = null;

const getWorker = () => {
  if (!heicWorker) {
    try {
      // The large worker code blob would be loaded from external file in production
      const workerCode =
        `// Worker code here - would be loaded from separate file`;
      const blob = new Blob([workerCode], { type: "application/javascript" });
      heicWorker = new Worker(URL.createObjectURL(blob));

      heicWorker.onerror = (error) => {
        logger.error("Worker initialization failed", "workerSetup", error);
        throw new HeicConversionError(
          "Worker failed to initialize",
          "workerSetup",
          error,
        );
      };
    } catch (error) {
      logger.error("Failed to create worker", "workerSetup", error);
      throw new HeicConversionError(
        "Worker creation failed",
        "workerSetup",
        error,
      );
    }
  }
  return heicWorker;
};

// Convert HEIC to image data using worker
const convertToImageData = (buffer) => {
  return new Promise((resolve, reject) => {
    try {
      const worker = getWorker();
      const messageId = (Math.random() * new Date().getTime()).toString();
      const message = { id: messageId, buffer };

      const handleMessage = (event) => {
        if (event.data.id === messageId) {
          worker.removeEventListener("message", handleMessage);
          worker.removeEventListener("error", handleError);

          if (event.data.error) {
            reject(
              new HeicConversionError(event.data.error, "workerConversion"),
            );
          } else {
            resolve(event.data.imageData);
          }
        }
      };

      const handleError = (error) => {
        worker.removeEventListener("message", handleMessage);
        worker.removeEventListener("error", handleError);
        reject(
          new HeicConversionError(
            "Worker communication failed",
            "workerConversion",
            error,
          ),
        );
      };

      worker.addEventListener("message", handleMessage);
      worker.postMessage(message);
      worker.addEventListener("error", handleError);
    } catch (error) {
      reject(
        new HeicConversionError(
          "Failed to send message to worker",
          "workerConversion",
          error,
        ),
      );
    }
  });
};

// Convert image data to canvas
const imageDataToCanvas = (buffer) => {
  return asyncGenerator("canvasConversion", null, function* () {
    try {
      const imageData = yield convertToImageData(buffer);
      const canvas = document.createElement("canvas");

      canvas.width = imageData.width;
      canvas.height = imageData.height;

      const context = canvas.getContext("2d");
      if (!context) {
        throw new HeicConversionError(
          "Failed to get canvas context",
          "canvasConversion",
        );
      }

      context.putImageData(imageData, 0, 0);
      return canvas;
    } catch (error) {
      throw new HeicConversionError(
        "Failed to convert image data to canvas",
        "canvasConversion",
        error,
      );
    }
  });
};

// Clean up canvas resources
const cleanupCanvas = (canvas) => {
  try {
    canvas.width = 1;
    canvas.height = 1;
    const context = canvas.getContext("2d");
    if (context) {
      context.clearRect(0, 0, 1, 1);
    }
  } catch (error) {
    logger.error("Canvas cleanup failed", "resourceCleanup", error);
  }
};

// Main HEIC conversion function
export const heicTo = (options) => {
  return asyncGenerator(
    "mainConversion",
    [options],
    function* (
      {
        blob,
        type = "image/jpeg",
        quality = 0.8,
        options: convertOptions = {},
      },
    ) {
      let canvas = null;

      try {
        // Validate inputs
        if (!blob) {
          throw new HeicConversionError("Blob is required", "inputValidation");
        }

        if (typeof quality !== "number" || quality < 0 || quality > 1) {
          throw new HeicConversionError(
            "Quality must be a number between 0 and 1",
            "inputValidation",
          );
        }

        const buffer = yield blob.arrayBuffer();

        if (type === "bitmap") {
          const imageData = yield convertToImageData(buffer);
          return createImageBitmap(imageData, convertOptions);
        } else {
          canvas = yield imageDataToCanvas(buffer);

          return yield new Promise((resolve, reject) => {
            try {
              canvas.toBlob(
                (result) => {
                  if (result != null) {
                    resolve(result);
                  } else {
                    reject(
                      new HeicConversionError(
                        "Canvas to blob conversion failed",
                        "blobConversion",
                      ),
                    );
                  }
                },
                type,
                quality,
              );
            } catch (error) {
              reject(
                new HeicConversionError(
                  "Canvas to blob conversion error",
                  "blobConversion",
                  error,
                ),
              );
            }
          });
        }
      } catch (error) {
        // Re-throw HeicConversionError as-is, wrap others
        if (error instanceof HeicConversionError) {
          throw error;
        }
        throw new HeicConversionError(error.message, "mainConversion", error);
      } finally {
        // Always clean up canvas resources
        if (canvas) {
          cleanupCanvas(canvas);
        }
      }
    },
  );
};

// Export error class for external error handling
export { HeicConversionError };